From: Sandy King (sanking@hubcap.clemson.edu)
Date: 08/05/00-09:52:20 PM Z
Hi Sil,
Thank you very much for your clear and helpful description for
precipitating Silver Oxide from Silver Nitrate. It now seems very simple!
Sandy King
>At 2000/08/05 09:59 PM -0400, Sandy wrote:
>>"Alternatively, 7 g Silver(I) Oxide may be precipitated from a solution of
>>10.3 g Silver Nitrate by adding a solution of 2.5 g Sodium Hydroxide; after
>>filtration and washing, the moist precipitate may be dissolved in the
>>Sulphamic Acid."
>>
>>I don't understand the concept of a chemical being "precipitated from"
>>another but I have on hand a large suppy of silve nitrate and would like to
>>give it a try. Can someone explain how I would do this in practice,
>>especially the part about filtering and washing?
>
>Silver oxide is insoluble in water, so when it is created from the reaction
>between the silver nitrate and sodium hydroxide, it first forms a rather
>gelatinous precipitate, which will settle at the bottom of the container so
>much of the liquid can be decanted. The problem is that the guck at the
>bottom contains both the silver oxide and sodium nitrate, so you must get
>rid of the latter. So you add water to dilute the liquid, pour the mixture
>into a paper filter, and then pour water several times over the stuff
>collected by the filter to get rid of much of the sodium nitrate. This
>crude method should remove most of the nitrate, but enough not to react
>with the rest of the formula. Don't try to remove it from the filter, as
>much will be imbedded in the paper fibers, but dissolve it with the
>sulfamic acid in the quantity specified in the formula.
>
>Incidentally, coffee filters should be good enough to do the job, if you
>can't get standard chem lab paper filters.
>
>One other observation: do not use "lye" as this grocery item includes many
>harmful impurities. The sodium hydroxide doesn't necessarily have to be
>"reagent" grade, but should as least be "purified" flakes or pellets.
>"Photographic" grade is fine.
>
>
>Sil Horwitz, FPSA
>Technical Editor, PSA Journal
>teched@psa-photo.org
>silh@earthlink.net
>Visit http://www.psa-photo.org/
>Personal page: http://home.earthlink.net/~silh/
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